Tension device for a sewing machine

ABSTRACT

A tension device adapted for the sewing machine including an assembly consisting of two nip forming members at least one of which rotates freely on its stud. An adjusting means is provided to tighten or loosen spring means by means of which the two nip forming members are always passed against one another. The tension is applied to the thread by a friction force produced by the rotation of the roll or rolls on their studs, whereby uneveness of the thread does not cause breaking of the thread and the skipping of stitches when the thread passes the nip.

United States Patent [191 Ono et al.

[ TENSION DEVICE FOR A SEWING MACHINE [75] Inventors: Takeshi Ono, Nagoya; Takashi Hirayama, Toyota; Kimihiko Yamamoto, Nagoya, all of Japan [73] Assignee: Aisin Seiki Kabushiki Kaisha,

Kariya, Aichi Pref., Japan [22] Filed: Feb. 3, 1971 [21] Appl. No.: 112,203

[30] Foreign Application Priority Data Feb. 9, 1970 Japan "45/1 1245 [52] US. Cl ..l12/254 [51] Int. Cl. ..D05b 47/00 [58] Field of Search ..1 12/254, 255, 79 A, 79 R; 242/151 [56] References Cited UNITED STATES PATENTS 2,954,865 10/1960 Hackney et al ..1 12/79 A lu l k ]March 20, 1973 1,581,093 .4/1926 Howie .u ..ll2/79A Primary Examiner-George 1,-1. Krizmanich Attorney-Pierce, Scheffler & Parker [5 7] ABSTRACT A tension device adapted for the sewing machine ineluding an assembly consisting of two nip forming members at least one of which rotates freely on its stud. An adjusting means is provided to tighten or loosen spring means by means of which the two nip forming members are always passed against one another. The tension is applied to the thread by a friction force produced by the rotation of the roll or rolls on their studs, whereby uneveness of the thread does not cause breaking of the thread and the skipping of stitches when the thread passes the nip.

3 Claims, 5 Drawing Figures Casas-Robert ..1 12/254 PATENTEUMARZO ma 3.721.205 SHEET 30F 3 TENSION DEVICE FOR A SEWING MACHINE BACKGROUND OF THE INVENTION This invention relates to a sewing machine equipped with a tension device which may maintain the tension of the thread constant regardless of the unevenness of the thread.

As used herein, the terms unevenness of the thread refer to nep, slub and the like which will undesirably cause the breaking of the thread or skipping of stitches during operation of the sewing machine.

In the tension device presently used in the sewing machine, the thread coming from the source of supply is tensioned by being run between discs which are pressed together by means of a spring. Adjustment of the tension is effected by tightening or loosening the springs by means of which the discs are pressed toward one another. It is difficult to obtain constant tension for the thread that is required in the sewing operation and to eliminate the breaking of thread and the skipping of the stitches. The reason for this difficulty is that every unevenness of the thread is exactly translated into an increase or decrease of the tension, since major tension is applied to the by relying on the friction of the thread relative to the discs.

SUMMARY OF THE INVENTION The present invention comprises a tension device mounted in a sewing machine which applies tension to the thread through a nip formed by two members in surface engagement therewith. At least one of said two members rotates freely on its stud or shaft. The device serves to apply tension to the thread relying almost entirely on friction produced by rotation of the roll or rolls on their studs. The nipping pressure applied to the members may be adjusted by manual operative means which are also provided by the present invention. The present invention further provides means to install the device within an unused area of the sewing machine.

The present invention avoids the drawbacks of prior art tension devices briefly outlined above by substituting at least one of the conventional discs with a roll free to rotate on its stud. The tension device of the present invention greatly reduces the breaking of the thread and the skipping of the stitches, since the unevenness of the thread does not cause any appreciable fluctuation of the friction but merely provides slightly higher or lower nip pressure which does not affect the friction.

It is an object of this invention to provide an improved tension device for the sewing machine.

It is another object of the invention to provide an improved device to apply substantially uniform tension to the thread regardless of the unevenness of the thread.

It is still another object of the invention to provide for a tension device that may be installed within the unused space of the arm so that any visible tangible obstruction will be eliminated.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an elevational view ofa machine embodying certain features of the invention, parts being shown broken away;

FIG. 2 is a perspective view of the upper portion of the arm of a sewing machine;

FIG. 3 is a perspective view of the tension device of the present invention showing the cover by dot and dash line as if formed of transparent material;

FIG. 4 is an enlarged sectional view taken substantially along line IV IV of FIG. 3;

FIG. 5 is an enlarged sectional view taken substantially along line V V of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention will be illustrated in the form it may take when applied to well-known and conventional sewing machine 1. Such a sewing machine may include a base 2 having usual hollow upright bracket 3 extending upwardly therefrom, the hollow arm 9 extending, in substantially usual manner, over base 2 to present the usual front bearing upright 4 immediately over the known needle plate (not shown) provided in the base 2. The upright 4 may provide bores or other suitable guides in which may slide pressure foot bar 5 and needle bar 6. A combined pulley-and-hand wheel 7 is attached to the shaft at the end thereof extending beyond the arm 9 and provides for association therewith of a belt or other suitable means for driving the machine.

The tension device of the invention now to be described is fixed at the undersurface of the cover 8 which is detachably fixed to the arm 9, so that the device is being inside the arm 9.

With reference to FIG. 3, a base plate 10 is secured to the undersurface of the cover 8 by means of bolts 11 screwed into internal screws formed in downwardlyprotruding projections 12 as shown in dot and dash line in FIG. 3 and particularly. in FIG. 4. In FIG. 3, the cover 8 is represented as if it was formed of transparent material such as glass or plastic. Each of the projections is of sufficient length to leave enough space for the device to be installed between the undersurface of the cover 8 and the base plate 10. From the preceding, it will be noted that the device to be described herein is within the arm 9 when installed, thereby eliminating any obstruction to the convenience of the operator.

An arm 13 is free to swing about one of the bolts 11 at the front side of the machine as will be seen in FIG. 3 and in the cross section of FIG. 4. A ring-like spacer 14 is interposed between the undersurface of the projection 12 and the base plate 10 as will be seen specifically in FIG. 4, surrounding the bolt 11 at the front side of the machine and being of slightly larger depth than that of the arm 13 so that the arm is free to swing about the spacer 14 when the base plate is bolted to the projection 12. Rolls 15 and 16 are both free to rotate on the respective studs 17 and 18 fastened to the base plate 10 and the arm 13. The known E-rings 19 assure positioning of the respective rolls on their studs. The base plate 10 is provided with a pair of upright brackets 21 and 22 between which a threaded bar 23 is supported as shown specifically in FIG. 5. The bar 23 is secured at one end to the upright bracket 22 by means of lock nut 24 cooperating with a shoulder 25 of the bar, while the other end of the bar fits, freelyin an aperture of the upright 21. For convenience, the fixed end of the bar 23 is received in a slot formed in the upright bracket 22 as shown in FIG. 3 by the broken line. Fitted with threads on the bar 23 is a member 26 occupying a bore 29 of a knob 30 free to rotate on the bar 23 and knurled to provide a better grip. The periphery of the member 26 is formed with a plurality of spaced radial notches 27 one of which atthe uppermost position in the illustration slidably engages with a key 28 axially formed on the internal surface of the bore 29 of the knob 30. A compression spring 31 is interposed between the shoulder of the member 26 and an upright bracket 32 extending from the swingable arm 13. A hole 33 in the bracket 32 has a-larger diameter than that of the bar 23 to allow thearm 13 to swing. It will be understood from the preceding that the member 26 is adjusted to determine the .force of the compression spring by rotating the knob forwardly or backwardly, thereby determining a nip pressure of-the rolls 15 and 16. The reason why a plurality of notches are formed on the periphery of the member 26 is that the force of the spring 31 is predetermined depending on the tolerance of the spring when installed. As will be seen in FIG. 5, there is provided a lug 34 sweged inwardly from the upright bracket 22 and slidably engaging with a circular groove 35 formed in the end face of the knob 30 and centered on the axis of rotation of the knob, so that rotation of the knob is ensured.

The base plate 10 is further provided with a pair of downwardly extending brackets 36 and 37 to which is secured a bar 38 at both its ends (see FIG. 3). Mounted on the bar 38 is a coil spring 39 one end of which is anchored to the bar 38 by means of slit 380 whereas the other end is free and extends upwardly and is then bent laterally to form a lateral portion 40. The torsibility of the spring 39 functions to always hold the thread under a desired tension during the sewing operation. The base plate 10 is still further provided with a guide 41 extending upwardly and is then bent laterally to form a similar lateral portion 42 past which the thread travels in sliding relation therewith. The free end of the lateral portion 42 is preferably provided with a further upwardly bent portion or stop 43. An ingress eye 44 and egress eye 45 are provided for guidance of the thread T respectively at the back and front sides of the machine so that the thread may be held in the nip formed by the rolls l and 16 during its travel. As will be seen in FIG. 3, the ingress eye 44 is carried by a supporting member 46 fixed to a suitable portion on the outer surface of the cover 8 at its back side by means of set screw 47 whereas the egress eye 45 is fixed to the inside surface of the cover. The reason why the egress eye is inside the arm 9 is that the aforesaid tangible visible obstruction to the convenience of the operator may be elliminated, whereas the ingress eye 44 is outside the cover 8 to provide a path of the thread T in cooperation with the supply bobbin B (FIG. 2). As shown in FIG. 2, the cover 8 is provided with a through slot 48 in an imaginary plane defined by the path of the thread to be described hereinbelow. The egress eye 45 and the ingress eye 44 are both positioned at corresponding ends of the slot 48 with their respective slots 49 and 55 aligned with the slot 48 to facilitate positioning the thread therein.

The thread coming from supply bobbin B travels through the ingress eye 44, to the roll assembly consisting of the rolls l5 and 16. The thread is nipped between the two rolls which have surface engagement therebetween. The thread then advances through the guide bracket 42 and lateral portion 40 to the egress eye 45 and thence to the known guide 50 shown in FIG. 1. The thread thereafter travels to the conventional pick up lever 51 and in turn to the needle. Both rolls l5 and 16 are preferably formed of or provided with an outer layer of slightly soft resilient polymer of desired flexibility and are knurled to form a better nip therebetween so that soft but non-slipping engagement may be provided for the thread with the surface of the rolls. Adjustment of tension of the thread is effected by tightening or loosening the spring 31 by means of which the rolls are always pressed toward one another. As will be seen in FIG. 2, the knob 30 protrudes beyond the cover 8 through a square hole 52 which is large enough to provide clearance for the knob to rotate. The knob 30 is provided on its end surface with a scale or numerical symbols 54 as shown in FIG. 3, for adjustment of the tension, by reading the scale in connection with an index 53 marked on the adjacent upper surface of the cover 8.

The arm 13 extends to protrude beyond the wall of the cover 8 through a hole 56 shown by the broken line in FIG. 3. The hole 56 is of sufficient length to allow the lever 13 to swing so that roll 16 may be disengaged from the other roll 15, threading up the device being thus readily performed.

The invention offers special advantages from the stand point of constant tension of the thread regardless of the unevenness thereof, which results from replacement of the conventional two disc assembly with the roll and roll or roll and stationary surface assembly. By selecting the material for and grinding of such stationary surface, at least one of the rolls as herein described may be replaced by a stationary member with approximately indentical function with that of the replaced roll. The stationary member need not be specifically illustrated here, since it will readily be substituted for the roll by any known manner. Since the thread travels without substantial slipping engagement with the nip forming members and the tension is substantially applied to the thread by running friction of the roll or rolls on their studs, the unevenness of the thread causes no appreciable fluctuation of this friction. The device is not as sensitive to the unevenness of the thread as the conventional disc assembly type and the tension of the thread is thus maintained substantially constant during operation.

We claim:

L The combination of a sewing machine and a tension device therefor, said sewing machine having an arm,

a cover member detachably fixed on the arm of the sewing machine,

a base plate fixed to the inside of said cover member and provided with a pivot,

a swingable arm mounted on said pivot,

a drag assembly comprising two nip forming members respectively carried by said base plate and said swingable arm, at least one of said nip forming members comprising a roll mounted for rotation about its axis, said nip forming members adapted to apply tensional force to sewing thread as it is drawn therethrough proportional to the drag established by said drag assembly and means for adjusting the nip pressure between said nip forming members.

2. The combination claimed in claim 1 wherein said resilient spring means disposed between said means to adjust the p P Comprises, threaded member and said swingable arm to a threaded bar Secured to Said base P produce nip pressure between said nip forming a rotatable knob mounted on said threaded bar, members a threaded member engaging the threads of said 5 3. The combination as claimed in claim 2 and threaded further comprising two spaced bracket members means associated with said rotatable knob and said threaded member for rotating Said member on Said mounted on said base plate, the ends of said threaded bar being supported by said bracket members.

threaded bar so as to be moved axially thereon, d 

1. The combination of a sewing machine and a tension device therefor, said sewing machine having an arm, a cover member detachably fixed on the arm of the sewing machine, a base plate fixed to the inside of said cover member and provided with a pivot, a swingable arm mounted on said pivot, a drag assembly comprising two nip forming members respectively carried by said base plate and said swingable arm, at least one of said nip forming members comprising a roll mounted for rotation about its axis, said nip forming members adapted to apply tensional force to sewing thread as it is drawn therethrough proportional to the drag established by said drag assembly and means for adjusting the nip pressure between said nip forming members.
 2. The combination claimed in claim 1 wherein said means to adjust the nip pressure comprises, a threaded bar secured to said base plate, a rotatable knob mounted on said threaded bar, a threaded member engaging the threads of said threaded bar, means associated with said rotatable knob and said threaded member for rotating said member on said threaded bar so as to be moved axially thereon, and resilient spring means disposed between said threaded member and said swingable arm to produce nip pressure between said nip forming members.
 3. The combination as claimed in claim 2, and further comprising two spaced bracket members mounted on said base plate, the ends of said threaded bar being supported by said bracket members. 